The goal of this observational study is to characterize the clinical features of metallo-β-lactamase-producing carbapenem-resistant Enterobacterales (MBL-CRE) colonization and subsequent infection in patients after allogeneic hematopoietic stem cell transplantation (HSCT). The study aims to estimate the incidence of perianal MBL-CRE colonization, the proportion of subsequent infections, the associated risk factors, mortality, and the underlying antibiotic resistance mechanisms.

The main questions this study seeks to answer are:

1. What is the incidence of perianal MBL-CRE colonization following allogeneic HSCT?
2. Among colonized patients, what proportion subsequently develop MBL-CRE infections?
3. What are the risk factors for colonization and infection, the patterns of antimicrobial resistance, and the mortality among infected patients? Participants will undergo perianal swab screening for CRE as part of their routine post-transplant care. MBL-CRE isolates identified from perianal swabs will undergo antimicrobial resistance genomic analysis to investigate bacterial transmission dynamics and resistance mechanisms.

Inclusion Criteria:

• Adult patients (≥18 years) who received allogeneic hematopoietic stem cell transplantation;

Exclusion Criteria:

• Engraftment failure.

Adult patients (≥18 years) who received allogeneic hematopoietic stem cell transplantation.